An undersampled receiver generally includes a downconversion subsystem that downconverts a radio frequency signal to a desired intermediate frequency. The resulting intermediate frequency signal is then undersampled by an analog-to-digital (A/D) converter. The undersampled receiver exploits aliasing in the sampling process to enable a lower sample rate of the A/D converter. One example of an undersampled receiver is disclosed in commonly owned and assigned U.S. Pat. No. 7,580,686, entitled ADAPTIVE PREDISTORTION METHOD AND ARRANGEMENT, which issued Aug. 25, 2009. Specifically, U.S. Pat. No. 7,580,686 discloses an undersampled Transmit Observation Receiver (TOR) as part of a power amplifier linearization architecture. An input signal of the transmitter is undersampled in the same manner as the undersampled TOR output to allow a direct comparison between the undersampled input signal of the transmitter and the undersampled TOR output to drive adaptation of predistortion in the transmitter to compensate for the nonlinearity of the power amplifier.
One issue with an undersampled receiver is that the undersampled receiver cannot be easily characterized across the entire input bandwidth of the undersampled receiver, particularly for wideband signals. More specifically, if the input bandwidth of the undersampled receiver spans multiple Nyquist zones of an A/D converter of the undersampled receiver, then images of the undersampled signal will overlap. As a result, multiple frequencies of an input signal of the undersampled receiver may alias into the same frequency in an output signal of the undersampled receiver. Due to this aliasing, the undersampled receiver is not easily characterized across the entire input bandwidth.